Piston type compressor

ABSTRACT

A piston type compressor comprises a housing, a rotary shaft supported by the housing, a cam mounted on the rotary shaft. The housing includes a discharge-pressure region and a suction-pressure region. The compressor further comprises an oil separator provided in the discharge-pressure region and an oil reservoir for storing lubricating oil from the oil separator. The rotary shaft has a regulating means for regulating the axial movement of the rotary shaft and for forming a clearance between the regulating means and the valve plate assembly. The clearance is communicated with the oil reservoir through a communication hole formed in the valve plate assembly so that the clearance functions as a throttle in an oil return passage extending from the oil separator to the inside of the compressor. A supply passage is formed in the rotary valve and in communication with the cam chamber in which a suction port is provided.

BACKGROUND OF THE INVENTION

The present invention relates to a piston type compressor having an oilseparator for separating lubricating oil from discharged refrigerantgas.

In a piston type compressor for a vehicle air conditioner, lubricatingoil in the form of mist is mixed with refrigerant gas for flowingtherewith within the compressor thereby to lubricate inner parts of thecompressor. In such a compressor, the oil is contained in the dischargedrefrigerant gas. To prevent oil from being carried by the refrigerantgas to an external refrigerant circuit of the vehicle air conditioner,an oil separator is provided in a discharge-pressure region within thecompressor for separating oil from the refrigerant gas. This is becausethe oil flowing with the refrigerant gas into the external refrigerantcircuit tends to adhere to an inner wall surface of a heat exchanger inthe external refrigerant circuit thereby to deteriorate the heatexchanging efficiency of the heat exchanger. A typical piston typecompressor having an oil separator is disclosed, for example, inJapanese Patent Application Publication No. 2004-218601.

The piston type compressor has such a structure in which oil separatedfrom refrigerant gas by the oil separator returns into the compressor(specifically, returns into a compression chamber) in order to keepefficient lubrication of inner parts of the compressor. For thispurpose, the oil separator and the interior of the compressor are incommunication through an oil return passage.

The oil return passage connects the oil separator with the compressionchamber, so that there is a pressure differential between the oilseparator and the compression chamber when the oil return passageconnects the compression chamber that has just completed the suctionstroke (namely, a suction-pressure region) with the oil separator(namely, a discharge-pressure region).

If the cross-sectional area of the oil return passage is excessivelylarge, not only the oil but high-pressure refrigerant gas dischargedinto the oil separator would flow back into the compression chamber anda large amount of refrigerant gas will leak from the oil separator tothe compression chamber. For this reason, the oil return passage shouldbe formed with an extremely small cross-sectional area or the oil returnpassage should have a throttle portion therein to provide a throttlefunction in the oil return passage, thereby preventing the refrigerantgas from flowing back.

In the structure having a throttle with an extremely smallcross-sectional area, however, foreign matters tend to clog the oilreturn passage and/or the throttle portion. If the foreign, matters clogthe oil return passage and/or the throttle portion, the quantity oflubricating oil that returns into the compressor through the oil returnpassage will be decreased, with the result that efficient lubrication ofthe compressor cannot be performed.

The present invention is directed to a piston type compressor thatprevents the leakage of refrigerant gas from a discharge-pressure regionto a suction-pressure region of the compressor and effectively returnslubricating oil to the suction-pressure region of the compressor.

SUMMARY OF THE INVENTION

In accordance with the present invention, a piston type compressorcomprises a housing, a rotary shaft supported by the housing, a cammounted on the rotary shaft. The housing is formed with a cylinder borein which a piston is accommodated and a cam chamber in which the cam isaccommodated. The housing is further provided with a discharge-pressureregion and a suction-pressure region therein. The compressor furthercomprises an oil separator provided in the discharge-pressure region andan oil reservoir for storing lubricating oil from the oil separator. Therotary shaft is provided with a regulating means for regulating theaxial movement of the rotary shaft and for forming a clearance betweenthe regulating means and the valve plate assembly. The clearance iscommunicated with the oil reservoir through a communication hole formedin the valve plate assembly so that the clearance functions as athrottle in an oil return passage extending from the oil separator tothe inside of the compressor. The rotary shaft may be provided with arotary valve. A supply passage as a suction passage is formed in therotary valve and in communication with the cam chamber in which asuction port is provided to be connected to an evaporator in an externalrefrigerant circuit.

Other aspects and advantages of the invention will become apparent fromthe following description, taken in conjunction with the accompanyingdrawings, illustrating by way of example the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention that are believed to be novel areset forth with particularity in the appended claims. The inventiontogether with objects and advantages thereof, may best be understood byreference to the following description of the presently preferredembodiments together with the accompanying drawings in which:

FIG. 1 is the longitudinal cross-sectional view of a piston typecompressor according to an embodiment; and

FIG. 2 is the partially enlarged cross-sectional view of a rotary valvearound a closure cap.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following will describe a preferred embodiment of a piston typecompressor according to the present invention with reference to FIGS. 1and 2. Note that the double-headed arrow Y1 indicates the upper andlower sides of a piston type compressor 10 and the double-headed arrowY2 indicates the front and rear sides of the compressor 10 in FIG. 1.

Now referring to FIG. 1, the piston type compressor 10 includes a fronthousing 12 and a rear housing 13 connected to the rear end of the fronthousing 12. A cylinder block 11 is fixedly connected inside the fronthousing 12. A valve plate assembly 14 is interposed between the cylinderblock 11 and the rear housing 13. The cylinder block 11, the rearhousing 13 and the valve plate assembly 14 are fastened together by aplurality of bolts B (only one bolt B shown in FIG. 1). The fronthousing 12 and the rear housing 13 cooperate to form the housingassembly of the compressor 10.

The housing assembly has a discharge chamber 18 formed between the rearhousing 13 and the valve plate assembly 14 on the radially outer side inthe rear housing 13. The rear housing 13 is provided with an oilseparator S for separating lubricating oil contained in refrigerant gas.The oil separator S is in fluid communication with the discharge chamber18 through a communication port 18 a. Hence, the oil separator S islocated in a discharge-pressure region of the compressor 10.

The oil separator S includes an oil separation chamber 44 and an oilseparation cylinder 45 accommodated in the oil separation chamber 44.The oil separation chamber 44 is in communication with the dischargechamber 18 through the communication port 18 a. The communication port18 a is opened to the oil separation chamber 44 at a position whichfaces the outer peripheral surface of the oil separation cylinder 45.

The oil separator S has a discharge hole 35 formed therein for allowingrefrigerant gas from which lubricating oil has been separated to bedischarged out from the compressor 10. The discharge chamber 18 is incommunication with an external refrigerant circuit 26 through thedischarge hole 35. The external refrigerant circuit 26 includes acondenser 27 for removing heat from refrigerant gas, an expansion valve28 and an evaporator 29 for transferring ambient heat in vehiclecompartment to refrigerant gas. The discharge hole 35 is incommunication with the condenser 27.

An oil reservoir T is formed at the center of the rear housing 13between the rear housing 13 and the valve plate assembly 14. The oilreservoir T and the oil separation chamber 44 of the oil separator S arein communication through an oil passage 32, through which lubricatingoil separated from refrigerant gas in the oil separator S is carriedinto the oil reservoir T for storage therein.

The oil reservoir T is in communication with a shaft hole 20, or thelike, at the center of the cylinder block 11 through a communicationhole 46 formed in the valve plate assembly 14, so that the lubricatingoil stored in the oil reservoir T flows back toward the cylinder block11 through the communication hole 46. Additionally, the valve plateassembly 14 has discharge ports 14 a and discharge valves 14 b formedtherein in association with the discharge chamber 18. The dischargevalves 14 b are operable to open and close the respective dischargeports 14 a. In this embodiment, the discharge chamber 18, the oilseparation chamber 44, the discharge hole 35, the oil reservoir T andthe compression chamber 34 in discharge stroke form thedischarge-pressure region of the compressor 10.

A crank chamber 17, which serves as a cam chamber, is defined betweenthe front housing 12 and the cylinder block 11. A rotary shaft 19 isrotatably supported in the crank chamber 17 by the cylinder block 11 andthe front housing 12. The rotary shaft 19 is inserted at one end thereofinto the shaft hole 20 formed in the cylinder block 11 and at the otherend thereof into a shaft hole 21 formed in the front housing 12. Theshaft hole 20 is located in alignment with the oil reservoir T throughthe valve plate assembly 14, and the communication hole 46 adjacent tothe cylinder block 11 is opened to the shaft hole 20.

The rotary shaft 19 is supported at its front side by the front housing12 through a radial bearing 22 placed in the shaft hole 21. The rotaryshaft 19 is directly supported at its rear side by the cylinder block 11through a peripheral sealing surface 20 a formed on the inner peripheralsurface of the shaft hole 20. Thus, the communication hole 46 adjacentto the cylinder block 11 is opened to the rear end of the rotary shaft19. The radial bearing 22 and the peripheral sealing surface 20 a of theshaft hole 20 receive radial loads on the front and rear sides of therotary shaft 19, respectively. A shaft seal 23 of a lip seal type isinterposed between the front housing 12 and the rotary shaft 19.

A swash plate 24 which serves as a cam is secured on the rotary shaft 19within the crank chamber 17. The swash plate 24 has at its boss portion24 a an inserting hole 24 b which is formed along the axis of the swashplate 24 (that is, along the axis L of the rotary shaft 19), and therotary shaft 19 is press-fitted in the inserting hole 24 b.

The crank chamber 17 is in communication with the evaporator 29 in theexternal refrigerant circuit 26 through a suction hole 25 formed in thefront housing 12. Refrigerant gas, which is discharged into thedischarge chamber 18 and the lubricating oil separated therefrom at theoil separator S, flows into the condenser 27 in the external refrigerantcircuit 26 through a discharge hole 35 adjacent to the oil separator S.After passing through the expansion valve 28 and the evaporator 29,refrigerant gas flows into the crank chamber 17 through the suction hole25. The shaft seal 23 prevents the leakage of refrigerant gas through aclearance between the peripheral surface of the rotary shaft 19 and thefront housing 12. A thrust bearing 30 is interposed between the fronthousing 12 and the boss portion 24 a of the swash plate 24 for receivingan axial load (or thrust load) of the rotary shaft 19.

A plurality of cylinder bores 11 a (five cylinder bores in thisembodiment but only one being shown in FIG. 1) are formed in thecylinder block 11 around the rotary shaft 19. Each of the cylinder bores11 a is closed by the valve plate assembly 14 and accommodates therein areciprocally slidable single-headed piston 31. Each piston 31 slidablyengages with the periphery of the swash plate 24 through a pair of shoes33 a, 33 b.

The rotation of the swash plate 24 with the rotary shaft 19 is convertedinto the reciprocal movement of the pistons 31 in the cylinder bore 11 athrough the shoes 33 a, 33 b. In other words, the pistons 31 areoperatively associated with the rotation of the rotary shaft 19 throughthe swash plate 24 secured to the rotary shaft 19. The pistons 31 andthe valve plate assembly 14 define compression chambers 34 in therespective cylinder bores 11 a. The shaft hole 20 of the cylinder block11 surrounded by the cylinder bores 11 a serves also as a valve chamber.The shaft hole 20 and the compression chambers 34 (cylinder bores 11 a)are in communication with each other through respective suction ports 36formed in the cylinder block 11. Each suction port 36 has an inlet 36 aopened at the peripheral sealing surface 20 a of the shaft hole 20 andan outlet 36 b opened at the inner peripheral surface of the cylinderbore 11 a.

As mentioned earlier, the rotary shaft 19 is rotatably received at therear end thereof (or the side thereof adjacent to the valve plateassembly 14) in the shaft hole 20. The rotary shaft 19 has a supplypassage 41 extending axially from the thrust bearing 30 to the rear endof the rotary shaft 19. An introducing hole 42 extends through the bossportion 24 a of the swash plate 24 and the rotary shaft 19 for fluidcommunication between the supply passage 41 and the crank chamber 17.That is, the introducing hole 42 permits refrigerant gas in the crankchamber 17 to flow into the supply passage 41.

An introducing port 43 is formed in the rotary shaft 19 adjacent to thevalve plate assembly 14 for communication with the supply passage 41.The introducing port 43 has an inlet 43 a which is opened at the innerperipheral surface of the rotary shaft 19 and an outlet 43 b which isopened at the outer peripheral surface of the rotary shaft 19. As therotary shaft 19 is rotated in operation of the compressor 10, the outlet43 b of the introducing port 43 communicates intermittently with theinlet 36 a of the suction port 36. The supply passage 41, theintroducing hole 42 and the introducing port 43 in the rotary shaft 19are provided to introduce refrigerant gas from the crank chamber 17 intothe compression chamber 34. The rear portion of the rotary shaft 19which is surrounded by the peripheral sealing surface 20 a of the shafthole 20 functions as a rotary valve 50 formed integrally with the rotaryshaft 19 adjacent to the valve plate assembly 14. In this embodiment,the crank chamber 17, the shaft hole 20, the supply passage 41 and thecompression chamber 34 in suction stroke form a suction-pressure regionof the compressor 10.

In the above compressor 10, during the suction stroke of the piston 31(or the stroke when the piston 31 moves frontward), the inlet 36 a ofthe suction port 36, which communicates with the cylinder bore 11 a,communicates with the outlet 43 b of the introducing port 43. Therefore,refrigerant gas in the supply passage 41 of the rotary shaft 19 is drawninto the compression chamber 34 in the cylinder bore 11 a through theintroducing port 43 and the suction port 36.

On the other hand, during the discharge stroke of the piston 31 (or thestroke when the piston 31 moves rearward), communication between theinlet 36 a of the suction port 36 that communicates with the cylinderbore 11 a and the outlet 43 b of the introducing port 43 is shut off.Thus, refrigerant gas in the compression chamber 34 is discharged intothe discharge chamber 18 through the discharge port 14 a while pushingand opening the discharge valve 14 b. Refrigerant gas thus dischargedinto the discharge chamber 18 flows into the oil separator S and thenfurther flows to the external refrigerant circuit 26 through thedischarge hole 35 of the separator S. Refrigerant that flows out to theexternal refrigerant circuit 26 returns to the crank chamber 17 of thecompressor 10 afterward.

Referring to FIG. 2, the rotary valve 50 has an opening at its rear end.A closure cap 51, which serves a closure means, is fitted to the rearend of the rotary valve 50 at a position that is closer to the valveplate assembly 14 than the introducing port 43. This closure cap 51includes a cylindrical and hollow cap portion 52 and a flange portion53. The flange portion 53 extends radially from the rear end peripheryof the cap portion 52. The flange portion 53 extends all around the capportion 52. The closure cap 51 is fitted in the rotary valve 50 by theportion 52 press-fitted into the supply passage 41. The closure cap 51is rotatable with the rotary valve 50. With the cap portion 52 fitted inthe supply passage 41, the flange portion 53 covers the entire end faceof the rotary valve 50 (or the rotary shaft 19).

The length of the cap portion 52 in the axial direction of the closurecap 51 is slightly shorter than the distance from the rear end of therotary valve 50 to the introducing port 43. In other words, theintroducing port 43 is not closed by the cap portion 52. In addition,the diameter of the cap portion 52 is slightly greater than the innerdiameter of the rotary valve 50 (that is, the inner diameter of therotary shaft 19 or the diameter of the supply passage 41).

Therefore, with the closure cap 51 fitted in the rotary valve 50, thecap portion 52 closes the supply passage 41 and is pressed against theperipheral surface of the supply passage 41 (or the inner peripheralsurface of the rotary shaft 19) thereby to form a sealing surface 55. Inother words, the cap portion 52 seals to prevent the leakage ofrefrigerant gas through the rear end of the rotary valve 50 from thesupply passage 41.

A clearance CL is formed between the valve plate assembly 14 and the endface 53 a of the flange portion 53 adjacent to the valve plate assembly,as shown in FIG. 2. This clearance CL is provided to prevent slidingcontact between the closure cap 51 and the valve plate assembly 14during operation of the piston type compressor 10.

The closure cap 51 also functions as a regulating means for regulatingthe axial sliding movement of the rotary shaft 19 to a specified amount.The rotary shaft 19 is movable slightly in its axial direction thoughthis axial sliding movement of the rotary shaft 19 in forward directionis so regulated that the boss portion 24 a of the swash plate 24contacts with the thrust bearing 30. When the compressor 10 is stopped(e.g. when a clutch for transmitting power from a drive source to therotary shaft 19 is just disengaged), the compression reaction force thatacts on the pistons 31 from the compression chambers 34 is decreasedrapidly, so that the rotary shaft 19 tends to slide axially rearward.However, such axial sliding movement of the rotary shaft 19 in arearward direction is regulated by the end face 53 a of the flangeportion 53 of the closure cap 51 to be brought into contact with thevalve plate assembly 14.

Depending on the depth of press-fitting of the portion 52 of the closurecap 51 into the supply passage 41 or the thickness of the flange portion53, the clearance CL between the end face 53 a and the valve plateassembly 14 may be adjusted. By the clearance CL so adjusted, the axialsliding movement of the rotary shaft 19 may be regulated to any desiredamount. Note that the clearance CL should preferably be as small aspossible to prevent the leakage of refrigerant gas. In this embodiment,the clearance CL is formed with a cross-sectional area smaller than thecommunication hole 46.

The communication hole 46 is formed in the valve plate assembly 14 forproviding communication between the oil reservoir T and the clearanceCL. That is, the communication hole 46 is opened at one end thereof tothe oil reservoir T and at the other end to the clearance CL. Theclearance CL is in communication with the communication hole 46 and hasa smaller cross-sectional area than the communication hole 46, so thatit functions as a throttle to prevent the refrigerant gas from flowingback from the oil separator S through the oil passage 32, the oilreservoir T and the communication hole 46. The end face 53 a of theflange portion 53 and the inner surface 52 a of the cap portion 52 (orthe end face thereof adjacent to the valve plate assembly 14) cooperateto form a surface receiving back pressure from the oil reservoir T.

In operation of the above-described piston type compressor 10,refrigerant gas discharged from the compression chamber 34 into thedischarge chamber 18 then flows into the oil separator S through thecommunication port 18 a. Refrigerant gas introduced into the oilseparation chamber 44 in the oil separator S is whirled in the spacebetween the inner peripheral surface of the oil separation chamber 44and the outer peripheral surface of the oil separations cylinder 45, andthe lubricating oil contained in the refrigerant gas is separatedtherefrom under the influence of centrifugal force. Refrigerant gas thelubricating oil is separated therefrom flows into the oil separationcylinder 45 through the bottom opening thereof and then flows out to theexternal refrigerant circuit 26 (specifically, to the condenser 27)through the discharge hole 35 formed at the top of the oil separationcylinder 45.

On the other hand, lubricating oil separated from refrigerant gas in theoil separation chamber 44 is conveyed to the oil reservoir T through theoil passage 32. Furthermore, lubricating oil stored in the oil reservoirT is supplied to the shaft hole 20 through the communication hole 46. Inother words, lubricating oil separated from refrigerant gas returns tothe shaft hole 20 from the oil separator S.

The oil separator S and the shaft hole 20 are in communication throughthe oil passage 32, the oil reservoir T and the communication hole 46.The communication hole 46 communicates with the clearance CL, whichfunctions as a throttle for the oil return passage extending from theoil separator S to the inner side of the compressor 10. Therefore,high-pressure refrigerant gas in the oil separator S is prevented fromleaking in large amount into the low-pressure shaft hole 20 which formsa part of a suction-pressure region of the compressor 10.

The closure cap 51 which rotates integrally with the rotary valve 50prevents the clearance CL from being clogged with foreign matters,thereby maintaining the clearance CL for constant communication betweenthe hole 46 and the shaft hole 20. Accordingly, there will not occur atrouble that the clearance CL clogs thereby to block the flow oflubricating oil returning from the oil separator S to the shaft hole 20.Thus, lubricating oil returned to the shaft hole 20 through theclearance CL is supplied between the outer peripheral surface 50 a ofthe rotary valve 50 and the peripheral sealing surface 20 a and furthersupplied into the crank chamber 17 along the rotary shaft 19. As aresult, lubricating oil circulates in the compressor 10, thus ensuringlubrication of its parts.

In addition, when lubricating oil returns from the oil reservoir T tothe shaft hole 20 through the communication hole 46, high pressure isapplied to the end face 53 a of the flange portion 53 and the innersurface 52 a of the cap portion 52 in the frontward axial direction. Asthe closure cap 51 is subjected to such back pressure at the end face 53a and the inner surface 52 a, the rotary shaft 19 to which the closurecap 51 is fitted is urged axially forward by the back pressure, that is,toward the crank chamber 17.

Subsequently, the swash plate 24 secured to the rotary shaft 19 is alsourged forward in the axial direction of the rotary shaft 19, and itsfront surface of the boss portion 24 a is entirely pressed against thethrust bearing 30. Urging the swash plate 24 against the thrust bearing30 prevents the swash plate 24 from being inclined by compressionreaction force via the pistons 31, otherwise the front face of the swashplate boss portion 24 a would be inclined by the reaction force withrespect to the thrust bearing 30, perpendicular to the axis of therotary shaft 19. This ensures the entire circumferential contact betweenthe front surface of the swash plate boss portion 24 a and the thrustbearing 30, and prevents their partial contact.

According to the preferred embodiment, the following advantageouseffects are obtained.

(1) The clearance CL which is formed between the valve plate assembly 14and the end of the closure cap 51 adjacent to the valve plate assembly14 is in communication with the oil reservoir T through thecommunication hole 46. The clearance CL functions as a throttle for theoil return passage which extends from the oil separator S, thedischarge-pressure region, to the shaft hole 46, the suction-pressureregion. Thus, the clearance CL restricts refrigerant gas in the oilseparator S to flow back to the shaft hole 20, thereby preventing alarge amount of refrigerant gas from leaking from the discharge-pressureregion to the suction-pressure region.

In addition, the closure cap 51 rotates integrally with the rotary valve50 (or the rotary shaft 19), so that the closure cap 51 which forms theclearance CL rotates relatively to the valve plate assembly 14. As aresult, the clearance CL will not be clogged with any foreign mattersmay be contained in lubricating oil and/or refrigerant gas. This keepsthe clearance CL free from blockage and ensures lubricating oil toreturn smoothly from the oil reservoir T through the communication hole46, thus appropriate lubrication within the compressor 10 is obtained.

(2) The clearance CL is formed between the closure cap 51 and the valveplate assembly 14 for allowing the slight axial movement of the rotaryshaft 19. This clearance CL is utilized as a throttle for the oil returnpassage from the oil separator S. Thus, the preferred embodimentprovides a structure made in a similar way for preventing the leakage ofrefrigerant gas from the discharge-pressure region to thesuction-pressure region, compared to, for example, the cross-sectionalarea of the communication hole 46 made small for the same purpose.

(3) The oil reservoir T and the shaft hole 20 are made in communicationwith each other through the communication hole 46 so that lubricatingoil in the oil reservoir T returns to the shaft hole 20(suction-pressure region) through the communication hole 46. Thus, backpressure in the oil reservoir T may be applied to the inner surface 52 aof the cap portion 52 and the end face 53 a of the flange portion 53.With the closure cap 51 subjected to the back pressure, the rear end ofthe rotary shaft 19 is urged toward the crank chamber 17. As a result,the swash plate 24 is pressed at the entire side surface of the bossportion 24 a thereof against the thrust bearing 30. Accordingly, theswash plate 24 is prevented from being inclined with respect to thethrust bearing 30 by compression reaction force acting on the pistons31. This prevents the front face of the swash plate boss portion 24 afrom partially pressing and contacting to the thrust bearing 30. Hence,rattling of the rotary shaft 19 causing the above partial press andcontact between the swash plate 24 and the thrust bearing 30 is reduced,thereby preventing generation of noise and vibration.

(4) The clearance CL is supplied and filled with lubricating oil fromthe oil reservoir T. Thus, leakage of refrigerant gas through theclearance CL is prevented.

(5) Means for closing the supply passage 41 of the rotary valve 50 isprovided as the closure cap 51 which is press-fitted in the supplypassage 41. The closure cap 51 is simply fitted to the rotary valve 50merely by press-fitting it into the supply passage 41. This simplifiesthe process of assembling the compressor 10.

(6) The closure cap 51 includes the cap portion 52 and the flangeportion 53. When the portion 52 of the closure cap 51 is press-fitted inthe supply passage 41, the flange portion 53 may contact with the axialrear end of the rotary valve 50 in order to limit its furtherpress-fitting into the supply passage 41 for the clearance CL not soenlarged.

(7) The closure cap 51 to receive the back pressure but also to serve asa regulating member for regulating the axial displacement of the rotaryshaft 19. This simplifies the structure of the compressor 10 incomparison to a structure in which components for respective functionsare provided individually.

The present invention is not limited to the above-described embodimentbut it may be modified into various alternative embodiments asexemplified below.

In an alternative embodiment, the cap portion 52 is not limited to ahollow structure, but it may be of solid provided that the cap portion52 press-fitted in a position closes the supply passage 41.

In an alternative embodiment, if the cap portion 52 press-fitted in aposition is prevented from moving further into the supply passage 41,the closure cap 51 may be formed only by the cap portion 52 without theflange portion 53.

In an alternative embodiment, the present invention is also applicableto a piston type compressor equipped with a cam having a shape otherthan that of the swash plate 24.

In an alternative embodiment, the oil separator S is not limited to acentrifugal separator, but it may be, for example, an inertial separatorfor separating lubricating oil from refrigerant gas by allowing therefrigerant gas to collide against a wall surface.

In an alternative embodiment, a filter may be provided in the oilreservoir T.

In an alternative embodiment, a cylindrical valve body having a bottomat one end may be fitted in the inserting hole 24 b of the swash plate24 for forming the rotary valve 50. In this case, the bottom of thevalve body closes the supply passage 41, and the clearance CL is formedbetween the bottom and the valve plate assembly 14. In other words, thebottom of the valve body may serve as a closure means, a pressurereceiving surface and a regulating means.

Therefore, the present examples and embodiments are to be considered asillustrative and not restrictive, and the invention is not to be limitedto the details given herein but may be modified within the scope of theappended claims.

1. A piston type compressor comprising: a housing having a plurality ofcylinder bores and a cam chamber, the housing being provided with adischarge-pressure region and a suction-pressure region therein; arotary shaft rotatably supported by the housing, the cylinder boresbeing arranged around the rotary shaft; a cam accommodated in the camchamber and rotatable integrally with the rotary shaft; a valve plateassembly provided between the cylinder bores and the discharge-pressureregion, the valve plate assembly having a communication hole thereon; apiston accommodated in each of the cylinder bores and operativelyconnected to the rotary shaft, the piston and the valve plate assemblydefining compression chamber in the respective cylinder bore; an oilseparator provided in the discharge-pressure region for separatinglubricating oil contained in refrigerant discharged from the compressionchambers; an oil reservoir formed in the discharge-pressure region tostore the lubricating oil separated by the oil separator, the oilreservoir being connected to the communication hole; and a regulatingmeans provided on the rotary shaft at an end position close to the valveplate assembly, the regulating means and the valve plate assemblyforming a clearance in-between, wherein the regulating means is alignedwith the communication hole so that the clearance is connected to theoil reservoir through the communication hole.
 2. The piston typecompressor according to claim 1 further comprising: a rotary valveformed integrally with the rotary shaft and located adjacent to thevalve plate assembly, the rotary valve having a supply passage and anintroducing port, the supply passage extending axially inside the rotaryvalve and being in communication with the introducing port, theintroducing port being capable of communicating with the cylinder borein which the piston is in suction stroke, the supply passage being openat the end surface of the rotary valve, wherein the regulating meansincludes a closure cap closing the open end of the supply passage on therotary valve.
 3. The piston type compressor according to claim 2,wherein the cam chamber is provided with a suction port connected to anevaporator in an external refrigerant circuit, the cam chamber beingconnected to the supply passage of the rotary valve.
 4. The piston typecompressor according to claim 2, wherein the closure cap is press-fittedin the supply passage.
 5. The piston type compressor according to claim4, wherein the closure cap includes: a cap portion press-fitted in thesupply passage; and a flange portion which extends radially from acircumferential end of the cap portion, wherein the clearance is formedbetween the flange portion and the valve plate assembly.
 6. The pistontype compressor according to claim 4, wherein the closure cap includes acylindrical and hollow cap portion press-fitted in the supply passage.7. The piston type compressor according to claim 1, further comprising:a thrust bearing provided for receiving axial load of the rotary shaft,wherein the regulating means has a surface for receiving pressure fromthe oil reservoir to urge the rotary shaft and the cam to the thrustbearing.
 8. The piston type compressor according to claim 1, wherein theoil separator is a centrifugal separator.
 9. The piston type compressoraccording to claim 1, wherein the compressor is of a fixed displacementtype.
 10. The piston type compressor according to claim 1, wherein theclearance is a throttle for a passage between the discharge-pressureregion and the suction-pressure region.